Electrocatalytic reactions on metallic surfaces are often modelled with density functional theory (DFT) in a plane-wave basis and employing periodic boundary conditions. With this approach, the electronic structure calculation is mostly limited to DFT with generalized gradient approximation functionals. In contrast, the reduced number of explicitly included atoms in embedding approaches allow to use more accurate electronic structure methods. Despite the obvious necessity that the embedding must account for all properties of the whole system that cannot be captured by the explicitly described region alone, it must be possible to describe the effect of an applied bias potential on the reaction energetics. We achieve this with a single-particle Green’s function embedding approach, where the embedding is modelled by two parameters only: an energy shift and a level broadening for each orbital of the boundary atoms. Since the density matrix of the embedded system is calculated via integration of this Green’s function, the molecule can be charged by tuning the upper integration limit. The embedding model is therefore grand-canonical with respect to the electrons and allows us to model the applied bias in an electrocatalytic reaction. We study this model on quasi-infinite one-dimensional systems: rings consisting of hydrogen, alkali, and earth-alkaline atoms. We analyze to what extent a proper choice of the two parameters allows us to mimic properties of the extended system like the total energy per monomer or the energy of the highest occupied molecular orbital. In silico studies of electrocatalytic reactions further require a solvent model that can describe the electrolyte solution. We recently implemented a non-linear Poisson–Boltzmann implicit solvation model and optimized the parameters of this model by fitting to experimental data in the form of Sechenov coefficients. In this contribution, we combine the grand-canonical cluster model with the implicit solvation model and study the vibrational Stark effect of carbon monoxide on metal surfaces in different electrolyte containing solvents and under applied bias. This is a crucial step toward the investigation of the role of the solvent and applied bias in electrocatalytic reactions from calculations with these embedded cluster models.

Toward the investigation of electrocatalysis with grand-canonical cluster models and implicit solvation

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.